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The use and re-use of N95 masks

A collaboration of Mumbai-based organisations has spawned a workable solution

In the case of infectious diseases like COVID-19, hospitals have to make sure that their patient-facing employees are safe by using Personal Protective Equipment, in particular, N95 masks. N95 masks can stop up to 95% of particles that are as small as 0.3 microns. Yet, not only are N95 masks expensive, they also cannot easily be reused immediately. A collaboration between Mumbai-based institutions, Tata Institute of Fundamental Research (TIFR) and Tata Memorial Hospital, has spawned a workable solution to the problem of expense and decontamination.

Moist heat

Chance and a shared interest in optimising the use of N95 masks brought together Arnab Bhattacharya, a TIFR professor, and C.S. Pramesh, the director of Tata Memorial Hospital. After discussing various routes for decontamination of the masks, such as the use of UV radiation, hydrogen peroxide and so on, they concluded that using moist heat was a good bet. They realised that heat treatment at temperatures beyond 65-70 degrees C for about 60 minutes in dry air or for just about 30 minutes in moist air with humidity over 50% was sufficient to decontaminate the masks, even with SARS-CoV-2 virus. In this method of decontamination, the pathogen is reduced by 99.9%. “We play safe and use 70 degrees C for more than 60 minutes, with some humidity anyway,” says Prof. Bhattacharya. “We have checked that the filtration efficiency of various masks is not impacted over five such one-hour decontamination cycles.”

Time, a decontaminant

If the used N95 mask is left alone and exposed to air for 96 hours, it will get decontaminated. If a person had five masks to use, and used a different one each day, then by the sixth day, the mask used on day one will be…

Shubashree Desikan

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